1 /* $OpenBSD: privsep.c,v 1.16 2006/10/25 20:55:04 moritz Exp $ */
2
3 /*
4 * Copyright (c) 2003 Can Erkin Acar
5 * Copyright (c) 2003 Anil Madhavapeddy <anil@recoil.org>
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 */
19
20 #include <sys/cdefs.h>
21 __FBSDID("$FreeBSD$");
22
23 #include <sys/types.h>
24 #include <sys/time.h>
25 #include <sys/socket.h>
26 #include <sys/ioctl.h>
27
28 #include <net/if.h>
29 #include <net/bpf.h>
30
31 #include <err.h>
32 #include <errno.h>
33 #include <fcntl.h>
34 #include <limits.h>
35 #include <pcap.h>
36 #include <pcap-int.h>
37 #include <pwd.h>
38 #include <signal.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <syslog.h>
43 #include <unistd.h>
44 #include "pflogd.h"
45
46 enum cmd_types {
47 PRIV_SET_SNAPLEN, /* set the snaplength */
48 PRIV_MOVE_LOG, /* move logfile away */
49 PRIV_OPEN_LOG /* open logfile for appending */
50 };
51
52 static int priv_fd = -1;
53 static volatile pid_t child_pid = -1;
54
55 volatile sig_atomic_t gotsig_chld = 0;
56
57 static void sig_pass_to_chld(int);
58 static void sig_chld(int);
59 static int may_read(int, void *, size_t);
60 static void must_read(int, void *, size_t);
61 static void must_write(int, void *, size_t);
62 static int set_snaplen(int snap);
63 static int move_log(const char *name);
64
65 extern char *filename;
66 extern pcap_t *hpcap;
67
68 /* based on syslogd privsep */
69 int
priv_init(void)70 priv_init(void)
71 {
72 int i, fd, socks[2], cmd;
73 int snaplen, ret, olderrno;
74 struct passwd *pw;
75
76 #ifdef __FreeBSD__
77 for (i = 1; i < NSIG; i++)
78 #else
79 for (i = 1; i < _NSIG; i++)
80 #endif
81 signal(i, SIG_DFL);
82
83 /* Create sockets */
84 if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1)
85 err(1, "socketpair() failed");
86
87 pw = getpwnam("_pflogd");
88 if (pw == NULL)
89 errx(1, "unknown user _pflogd");
90 endpwent();
91
92 child_pid = fork();
93 if (child_pid < 0)
94 err(1, "fork() failed");
95
96 if (!child_pid) {
97 gid_t gidset[1];
98
99 /* Child - drop privileges and return */
100 if (chroot(pw->pw_dir) != 0)
101 err(1, "unable to chroot");
102 if (chdir("/") != 0)
103 err(1, "unable to chdir");
104
105 gidset[0] = pw->pw_gid;
106 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
107 err(1, "setresgid() failed");
108 if (setgroups(1, gidset) == -1)
109 err(1, "setgroups() failed");
110 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1)
111 err(1, "setresuid() failed");
112 close(socks[0]);
113 priv_fd = socks[1];
114 return 0;
115 }
116
117 /* Father */
118 /* Pass ALRM/TERM/HUP/INT/QUIT through to child, and accept CHLD */
119 signal(SIGALRM, sig_pass_to_chld);
120 signal(SIGTERM, sig_pass_to_chld);
121 signal(SIGHUP, sig_pass_to_chld);
122 signal(SIGINT, sig_pass_to_chld);
123 signal(SIGQUIT, sig_pass_to_chld);
124 signal(SIGCHLD, sig_chld);
125
126 setproctitle("[priv]");
127 close(socks[1]);
128
129 while (!gotsig_chld) {
130 if (may_read(socks[0], &cmd, sizeof(int)))
131 break;
132 switch (cmd) {
133 case PRIV_SET_SNAPLEN:
134 logmsg(LOG_DEBUG,
135 "[priv]: msg PRIV_SET_SNAPLENGTH received");
136 must_read(socks[0], &snaplen, sizeof(int));
137
138 ret = set_snaplen(snaplen);
139 if (ret) {
140 logmsg(LOG_NOTICE,
141 "[priv]: set_snaplen failed for snaplen %d",
142 snaplen);
143 }
144
145 must_write(socks[0], &ret, sizeof(int));
146 break;
147
148 case PRIV_OPEN_LOG:
149 logmsg(LOG_DEBUG,
150 "[priv]: msg PRIV_OPEN_LOG received");
151 /* create or append logs but do not follow symlinks */
152 fd = open(filename,
153 O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW,
154 0600);
155 olderrno = errno;
156 send_fd(socks[0], fd);
157 if (fd < 0)
158 logmsg(LOG_NOTICE,
159 "[priv]: failed to open %s: %s",
160 filename, strerror(olderrno));
161 else
162 close(fd);
163 break;
164
165 case PRIV_MOVE_LOG:
166 logmsg(LOG_DEBUG,
167 "[priv]: msg PRIV_MOVE_LOG received");
168 ret = move_log(filename);
169 must_write(socks[0], &ret, sizeof(int));
170 break;
171
172 default:
173 logmsg(LOG_ERR, "[priv]: unknown command %d", cmd);
174 _exit(1);
175 /* NOTREACHED */
176 }
177 }
178
179 _exit(1);
180 }
181
182 /* this is called from parent */
183 static int
set_snaplen(int snap)184 set_snaplen(int snap)
185 {
186 if (hpcap == NULL)
187 return (1);
188
189 hpcap->snapshot = snap;
190 set_pcap_filter();
191
192 return 0;
193 }
194
195 static int
move_log(const char * name)196 move_log(const char *name)
197 {
198 char ren[PATH_MAX];
199 int len;
200
201 for (;;) {
202 int fd;
203
204 len = snprintf(ren, sizeof(ren), "%s.bad.%08x",
205 name, arc4random());
206 if (len >= sizeof(ren)) {
207 logmsg(LOG_ERR, "[priv] new name too long");
208 return (1);
209 }
210
211 /* lock destinanion */
212 fd = open(ren, O_CREAT|O_EXCL, 0);
213 if (fd >= 0) {
214 close(fd);
215 break;
216 }
217 /* if file exists, try another name */
218 if (errno != EEXIST && errno != EINTR) {
219 logmsg(LOG_ERR, "[priv] failed to create new name: %s",
220 strerror(errno));
221 return (1);
222 }
223 }
224
225 if (rename(name, ren)) {
226 logmsg(LOG_ERR, "[priv] failed to rename %s to %s: %s",
227 name, ren, strerror(errno));
228 return (1);
229 }
230
231 logmsg(LOG_NOTICE,
232 "[priv]: log file %s moved to %s", name, ren);
233
234 return (0);
235 }
236
237 /*
238 * send the snaplength to privileged process
239 */
240 int
priv_set_snaplen(int snaplen)241 priv_set_snaplen(int snaplen)
242 {
243 int cmd, ret;
244
245 if (priv_fd < 0)
246 errx(1, "%s: called from privileged portion", __func__);
247
248 cmd = PRIV_SET_SNAPLEN;
249
250 must_write(priv_fd, &cmd, sizeof(int));
251 must_write(priv_fd, &snaplen, sizeof(int));
252
253 must_read(priv_fd, &ret, sizeof(int));
254
255 /* also set hpcap->snapshot in child */
256 if (ret == 0)
257 hpcap->snapshot = snaplen;
258
259 return (ret);
260 }
261
262 /* Open log-file */
263 int
priv_open_log(void)264 priv_open_log(void)
265 {
266 int cmd, fd;
267
268 if (priv_fd < 0)
269 errx(1, "%s: called from privileged portion", __func__);
270
271 cmd = PRIV_OPEN_LOG;
272 must_write(priv_fd, &cmd, sizeof(int));
273 fd = receive_fd(priv_fd);
274
275 return (fd);
276 }
277 /* Move-away and reopen log-file */
278 int
priv_move_log(void)279 priv_move_log(void)
280 {
281 int cmd, ret;
282
283 if (priv_fd < 0)
284 errx(1, "%s: called from privileged portion\n", __func__);
285
286 cmd = PRIV_MOVE_LOG;
287 must_write(priv_fd, &cmd, sizeof(int));
288 must_read(priv_fd, &ret, sizeof(int));
289
290 return (ret);
291 }
292
293 /* If priv parent gets a TERM or HUP, pass it through to child instead */
294 static void
sig_pass_to_chld(int sig)295 sig_pass_to_chld(int sig)
296 {
297 int oerrno = errno;
298
299 if (child_pid != -1)
300 kill(child_pid, sig);
301 errno = oerrno;
302 }
303
304 /* if parent gets a SIGCHLD, it will exit */
305 static void
sig_chld(int sig)306 sig_chld(int sig)
307 {
308 gotsig_chld = 1;
309 }
310
311 /* Read all data or return 1 for error. */
312 static int
may_read(int fd,void * buf,size_t n)313 may_read(int fd, void *buf, size_t n)
314 {
315 char *s = buf;
316 ssize_t res, pos = 0;
317
318 while (n > pos) {
319 res = read(fd, s + pos, n - pos);
320 switch (res) {
321 case -1:
322 if (errno == EINTR || errno == EAGAIN)
323 continue;
324 case 0:
325 return (1);
326 default:
327 pos += res;
328 }
329 }
330 return (0);
331 }
332
333 /* Read data with the assertion that it all must come through, or
334 * else abort the process. Based on atomicio() from openssh. */
335 static void
must_read(int fd,void * buf,size_t n)336 must_read(int fd, void *buf, size_t n)
337 {
338 char *s = buf;
339 ssize_t res, pos = 0;
340
341 while (n > pos) {
342 res = read(fd, s + pos, n - pos);
343 switch (res) {
344 case -1:
345 if (errno == EINTR || errno == EAGAIN)
346 continue;
347 case 0:
348 _exit(0);
349 default:
350 pos += res;
351 }
352 }
353 }
354
355 /* Write data with the assertion that it all has to be written, or
356 * else abort the process. Based on atomicio() from openssh. */
357 static void
must_write(int fd,void * buf,size_t n)358 must_write(int fd, void *buf, size_t n)
359 {
360 char *s = buf;
361 ssize_t res, pos = 0;
362
363 while (n > pos) {
364 res = write(fd, s + pos, n - pos);
365 switch (res) {
366 case -1:
367 if (errno == EINTR || errno == EAGAIN)
368 continue;
369 case 0:
370 _exit(0);
371 default:
372 pos += res;
373 }
374 }
375 }
376